Marking device

ABSTRACT

A marking device having a nozzle orifice through which a fluid marking agent is forcibly ejected under pressure for marking an article spaced a distance therefrom. The orifice nozzle is carried on a housing and connected to a reservoir of the fluid marking agent contained therein. The housing includes a pumping element shiftably mounted within the reservoir for separating a portion of the fluid marking agent from the reservoir and pressurizing the separated fluid to forcibly eject a selected amount thereof through the orifice nozzle to mark the article.

United States Patent Abrams et al.

[ 1 Apr. 4, 1972 [54] MARKING DEVICE [72] Inventors: Paul S. Abrams, Huntington Woods; Ru-

dolph G. Peterson, Detroit, both of Mich.

[73] Assignee: Carco, lnc., Detroit, Mich.

[22] Filed: Jan. 13, 1970 [21] Appl. No.: 2,469

Related US. Application Data [63] Continuation-in-part of Ser. No. 817,371, Apr. 18,

1969, Pat. No. 3,614,940.

[52] US. Cl ..239/93, 239/101, 239/571 [51] Int. Cl. ..G0ld 15/18 [58] Field oiSearch... ....239/93,96,99, 101,570,571,

[56] References Cited UNITED STATES PATENTS 2,302,062 11/1942 Schweyer ..401/l76 X 2,496,804 2/1950 Meitzler 2,628,866 2/1953 Purcas, Jr. et a1 ..239/93 X 2,912,169 11/1959 Peffer, Jr. ..239/570 X 3,371,350 2/1968 Sanderson et a] ..346/140 3,520,477 7/1970 Cooley ..239/l0l 2,512,743 7/1950 Hansel]. .346/75 UX 3,296,624 l/1967 Ascoli.... .....346/l40 2,268,876 1/1942 Kagley ..l18/3 Primary Examiner-Lloyd L. King Assistant Examiner-Reinhold W. Thieme Attorney-Hauke, Gifford and Patalidis [5 7] ABSTRACT A marking device having a nozzle orifice through which a fluid marking agent is forcibly ejected under pressure for marking an article spaced a distance therefrom. The orifice nozzle is carried on a housing and connected to a reservoir of the fluid marking agent contained therein. The housing includes a pumping element shiftably mounted within the reservoir for separating a portion of the fluid marking agent from the reservoir and pressurizing the separated fluid to forcibly eject a selected amount thereof through the orifice nozzle to mark the article.

8 Claims, 3 Drawing Figures MARKING DEVICE CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of application Ser. No. 817,371, filed April I8, 1969, and now US. Pat. No. 3,614,940.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to marking devices and more particularly to such devices capable of marking an article spaced a distance therefrom.

II. Description of the Prior Art In our aforementioned patent, a novel marking device useful in industrial applications for marking a series of metal workpieces or the like with a pigmented ink is disclosed. This marking device comprises a housing for storing a liquid marking agent in a reservoir and includes a reciprocally mounted feed tube having its inner end extending into the reservoir and its opposite end terminating in a felt or similar nib. The feed tube is spring biased toward a normally extended position and is retracted during each marking stroke when the marking nib engages a workpiece. During the retracting stroke the feed tube engages a plunger fixedly mounted within the reservoir which pumps a charge of the fluid marking agent into the feed tube and into the marking nib to mark the engaged workpiece.

Although the marking device of the aforementioned patent provides certain new improvements, the present invention represents still another advance in the field of marking devices.

There are many industrial applications where, for various reasons, a felt tip impact type of marker such as the marking device of our aforesaid patent application is not desirable, for example, in situations where it is inconvenient to stop movement of the products to be marked at the marking station, such as parts on a conveyor line, or parts moving without a conveyor, as for example automotive wrist pins that are rolling down a ramp at a substantial production speed and may not be stopped to be marked.

Still other applications require the use of a very fast drying ink for random intermittent marking where the intervals between markings may be quite lengthy and a felt tip impact type of marker would tend to dry out between the markings. It would therefore be desirable to provide a marking device capable of marking an article from a distance without actual contact therewith and which will not dry out during lengthy intervals between markings.

SUMMARY OF THE INVENTION The present invention which will be subsequently described in greater detail comprises a housing having an internal reservoir for containing a supply of a fluid marking agent which is in fluid communication with the inlet of a feed passage whose outlet terminates in a nozzle orifice externally of the housing. A pumping element disposed within the reservoir is actuatable to engage the inlet of the feed passage to close off fluid communication between the reservoir and the feed passage so as to separate a portion of the fluid from the reservoir to pressurize the separated fluid within the feed passage to forcibly eject a selected portion of the separated fluid through the nozzle orifice with a sufficient force to carry the ejected fluid from the nozzle orifice to mark an article which is spaced a distance from the nozzle orifice.

A spring biased check valve within the feed passage is adapted to prevent fluid communication between the feed passage inlet and the nozzle orifice in the absence of pressure at the feed passage inlet. The check valve is opened by fluid pressure created by the pumping element as the same pressurizes the fluid within the inlet portion of the feed passage. The check valve is provided with passages so arranged that it has self-cleaning characteristics similar to those disclosed with respect to the valve means in our aforementioned patent.

The pumping element is so carried within the reservoir that a portion of the force created by the pumping element to produce a surge of pressure in the feed passage agitates the remaining fluid within the reservoir. This has the desirable effect of maintaining the pigmented ink, which forms the marking agent, in solution.

It is therefore an object of the present invention to provide an improved marking device having a pumping element therein which is adapted to pressurize a selected portion of a fluid marking agent contained within the marking device to eject the same therefrom to markan article spaced a distance therefrom.

Other objects, advantages and applications of the present invention will become apparent to those skilled in the art when the accompanying description of one example of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS The description herein refers to the accompanying drawings in which like reference characters refer to i like parts throughout the several views and in which:

FIG. 1 is a longitudinal partially sectioned view of a marking device embodying the present invention with the pumping element thereof in a retracted position;

FIG. 2 is a fragmentary sectional view of the marking device illustrated in FIG. 1 showing the pumping element thereof in an extended position; and

FIG. 3 is a sectional view of the device taken along line 3-3 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, and particularly FIG. I, there is illustrated a preferred marking device 10 comprising a cylindrical housing 11 having a cover 12 secured thereto by screws 13. The housing 11 is mounted on one leg 14 of a support base 15, while an air operated cylinder 16 that is axially aligned with the housing 11 is mounted on another leg 18 of the support base 15 The support base is adapted to be fastened proximate the articles (not shown) to be marked.

The air operated cylinder 16 is of the conventional type having a piston member (not shown) mounted therein for reciprocal movement in response to fluidpressure admitted through inlet ports 20 and 22. An actuating rod 24 connected to the piston member (not shown) of the air cylinder moves with the piston and engages a stem 26 of a pumping element 28 which is slidably mounted within a longitudinal bore 30 formed within the marking device 10 to actuate the pumping element 28 in a manner which will be explained in greater detail hereinafter.

Since the air operated cylinder 16 is of a conventional type commercially available, a further detailed description thereof is not necessary.

The longitudinal bore 30 of the marking device 10 communicates with a decreased diameter bore 32 which forms an inlet 34 of a feed passage 36, the outlet of which terminates in a nozzle orifice 38 formed in a nozzle housing 37 carried externally of the housing 11 of the marking device 10. Downstream of the inlet 34 a decreased section 35 of the feed passage 36 forms a conically shaped valve seat 40 on which a conical end 42 of a floating cylindrically shaped valve member 44 is normally seated. The particular shape of the valve member 44 and the valve seat 40 produce a self-cleaning action during movement of the valve member 44 in the same manner as the similar valve means of our aforementioned patent. The valve member 44 has an internal passage 46 which is opened at its downstream end 45 with the feed passage 36 which in turn communicates with the nozzle orifice 38 by an axial bore 39 within the nozzle housing 37. The passage 46 is connected at its upstream end to the feed passage 36 by a transverse passage 48. The valve member 44 is movable between an upstream position where it is seated on the valve seat 40 to close communication between the feed passage inlet 34 and that portion of the feed passage 36 downstream of the valve seam 40; and an open position in which the downstream end 45 of the valve member 44 abuts the nozzle 37 such that the path of fluid communication between the feed passage inlet 34 and the nozzle 38 is through the transverse passages 48, the internal passage 46 of the valve 44 and the axial bore 39 within the nozzle housing 37. The fluid is then ejected externally of the device by means of the nozzle orifice 38. The valve 44 is unseated and positioned in its downstream position when pressure acts on the conically shaped end 42 in a manner to be described hereinafter. A spring 50 positioned within the axial bore 39 of the nozzle housing 37 and the internal passageway 46 biases the valve member 44 towards its upstream position wherein the conical end 42 seats against the valve seat 40 to close communication between the feed passage inlet 34 and that portion of the feed passage 36 downstream of the valve seat 40.

A portion of the longitudinal bore 30 of the device adjacent the inlet 34 of the feed passage 36 forms a reservoir 52 for containing a quantity of a fluid marking agent. The fluid within the reservoir 52 is replenished by an external reservoir indicated schematically at 54 through an inlet 56.

The pumping element 28 comprises an elongated rod having an enlarged section 58 which slidably engages bore 30, and which is connected to stem 26 to produce reciprocal movement of the pumping element 28 in response to movement of the actuating rod 24 of the air cylinder 16. The inner end of the pumping element 28 forms a piston member 60 which is movable between a retracted position as illustrated in FIG. 1 wherein it is spaced from the inlet 34 of the feed passage 36 and fluid within the reservoir 52 is freely communicable to the feed passage 36; and an extended position in which the piston member 60 enters the feed passage inlet 34 to close communication between the feed passage 36 and the reservoir 52 thereby separating a slug of fluid within the feed passage 36 from the reservoir 52. The piston element 60 is ofa cylindrical shape complementary to the shape of the bore 32 and is so sized that when the same engages the bore 32 there is a fluid seal between the outer periphery of the piston 60 and the inner surface of the bore 32 so that fluid trapped within feed passage 36 will not leak back into the reservoir 52. As the piston member 60 is stroked to its extended position, it will raise the pressure of the trapped marking fluid within the feed passage 36 so as to generate a force of sufficient magnitude to move the valve member 44 off the seat 40 against the bias of the spring 50. The charge of marking fluid delivered under pressure into the transverse passages 48 and the internal passage 46 of the valve 44, and into the bore 39 of the nozzle 37 and externally of the marking device 10 through the nozzle orifice 38 to mark the article which is spaced from the nozzle orifice 38.

A spring 62, disposed within the reservoir 52 between a shoulder 64 of the housing and the enlarged section 58 of the pumping element 28, biases the pumping element and thus the piston 60 away from the feed passage inlet 34 to return the piston to its retracted position as illustrated in FIG. I. As the piston 60 returns to its retracted position, the communication between the feed passage inlet 34 and the reservoir 52 is opened and the amount of fluid ejected from the marking device is replenished therein. At the same time, spring 50 acts against the valve member 44 to cause it to engage seat 40, thereby preventing a return of fluid from the nozzle end of the feed passage 36 to the reservoir 52. The movement of the pumping element 28 between its retracted and its extended position sufficiently agitates the fluid marking agent within the reservoir 52 so that the pigmented ink therein remains in solution.

The stem 26 of the pumping element extends outwardly through a bore 68 in the cover 12 and has a threaded surface on which nut 70 engages. By varying the position of the nut 70 along the threaded surface of the stem 26 the amount of stroke of the pumping element 28 can be controlled as the inward movement of the pumping element 28 to its extended position will be limited by the abutment of the inner surface of the nut 70 against the outer surface of the cover 12. This, of course, will vary the degree of extension of the piston 60 into the feed passage 36 and in this way the force and amount of ink discharged through the orifice 38 can be controlled.

A pin 72 may be inserted between the inner end of the nut 70 to engage the threaded surface of the stem 26 to limit inward movement of the pumping element 28 towards its extended position by engagement of the inner surface of the pin 72 with the outer surface of the cap 12. The marking device will then function in its normal manner, however during certain applications the marking device may sit idle for a sufficient period of time for the ink in the nozzle orifice to dry. To return the marking device 10 to proper functioning the pin 72 would be removed so as to provide for a longer stroke of the pumping element and to thereby generate a higher pressure within the feed passage 36 to blow the dry ink out of the orifice nozzle 38. By simply replacing the pin 72 to its initial position on the stem 26 adjacent the nut 70 the original setting of the device is obtained without having to readjust the nut 70. Thus, means are provided for temporarily extending the stroke of the pumping element 28 without interfering with the adjusted stroking length.

In operation, the pumping element 28 is normally in the retracted position as illustrated in FIG. 1. When it is desired to forcibly eject a selected amount of fluid through the orifice nozzle 38 so as to mark an article which is spaced a selected distance from the nozzle, air pressure of approximately pounds per square inch is admitted into the inlet port 22 of the air cylinder 16 to cause the piston therein and thus the actuating rod 24 to be shifted leftwardly so as to engage the stem 26 of the pumping element 28 and drive the same leftwardly. When the piston member 60 of the pumping element 28 is driven leftwardly into its extended position as illustrated in FIG. 2, the same enters the feed passage bore 32 to close communication between the feed passage inlet 34 and the reservoir 52 thereby trapping a charge of the fluid marking agent therein. As the piston member 60 traverses the bore 32 toward the end of its stroke (which is determined by the positioning of the nut up on the stem 68), the pressure of the fluid within the bore 32 is raised to a sufficient level so as to move the valve member 44 off the seat 40 against the bias of the spring 50, whereby fluid enters the transverse inlet 48 and the internal passage 46 of the valve 44 and is discharged from the marking device through the orifice nozzle 38 as hereinbefore described. As soon as the air pressure in the air cylinder 16 is reduced through suitable valving means (not shown) the spring 62 within the fluid reservoir 52 exerts a force against the pumping element 28 to return the pumping element and the air cylinder to its fully retracted position as illustrated in FIG. 1 whereby fluid communication between the reservoir 52 and the inlet 34 of the feed passage 36 is again opened, and the marking device is again ready to commence another stroke to provide fluid to mark the articles as they pass the nozzle orifice 38.

It is apparent that a marking device has been described which permits marking of articles in industrial applications or the like where it is impossible or inconvenient to stop the article's movement long enough to produce a mark. With the marker of the present invention, the cylinder can be actuated either manually or through suitable sensing means to mark the articles as they move past the device.

Since there are no nibs to dry out, the present device can remain unused for longer periods of time than ordinary marking devices. If the ink should dry and clog the nozzle, the dry ink can usually be blown out by removing the pin 72 and operating the device a couple of times at the increased pressure produced by the longer stroke.

Thus it is apparent that an improved marking device has been described.

Having thus described the invention, what is claimed is as follows:

l. A device for forcibly ejecting a fluid marking agent for marking an article spaced a distance therefrom comprising:

a housing having a reservoir of said fluid marking agent;

a feed passage having an inlet in fluid communication with said reservoir and an outlet through which said fluid marking agent is forcibly ejected from said housing;

means for closing fluid communication between said reservoir and said feed passage for separating the fluid in said feed passage for forcibly ejecting a selected amount of said separated fluid through said feed passage outlet, said means comprising a piston member movably mounted within said reservoir between a first position in which said piston member engages the inlet of said feed passage to close fluid communication between said reservoir and said feed passage; and a second position in which said piston member is spaced from said inlet to permit fluid communication between said reservoir and said feed passage;

means normally biasing said piston member toward said second position; and including means for selectively varying the degree of extension of said piston member into said feed passage inlet when said piston memberis in said first position;

said last mentioned means comprising a stem member carried by said piston member and extending externally of said housing and means removably attached to said stem member externally of said housing, the degree of extension of said piston into said feed passage inlet being limited by the abutment of said removably attached means against said housing.

2. A device for forcibly ejecting a fluid marking agent for marking an article spaced a distance therefrom comprising:

a housing having a reservoir of said fluid marking agent;

a feed passage having an inlet in fluid communication with said reservoir and an outlet through which said fluid marking agent is forcibly ejected from said housing;

means for closing fluid communication between said reservoir and said feed passage for separating the fluid in said feed passage for forcibly ejecting a selected amount of said separated fluid through said feed passage outlet, said means comprising a piston member movably mounted within said reservoir between a first position in which said piston member engages the inlet of said feed passage to close fluid communication between said reservoir and said feed passage; and a second position in which said piston member is spaced from said inlet to permit fluid communication between said reservoir and said feed passage;

means normally biasing said piston member toward said second position; and including means for selectively varying the degree of extension of said piston member into said feed passage inlet when said piston member is in first position;

said feed passage inlet having a cross-sectional area less than the cross-sectional area of said reservoir;

said piston having a shape complementary to the shape of said feed passage inlet;

said feed passage inlet and said piston member being in axial alignment whereby said piston extends into and engages said feed passage inlet when said piston is in said first position, the amount of fluid ejected from said feed passage outlet being a function of the degree of extension of said piston member into said feed passage inlet at said first position of said piston, and

an enlarged portion carried by said piston member, said enlarged portion extending into said reservoir and adapted to agitate the fluid marking agent contained therein when said piston member is moved to said first position.

3. A device for forcibly ejecting a fluid marking agent for marking an article spaced a distance therefrom comprising:

a housing having a reservoir for said fluid marking agent and an inlet connected with said reservoir and adapted to be connected with a source of fluid marking agent; a feed passage axially aligned with said reservoir and communicating therewith, said feed passage being of a reduced cross section as compared with said reservoir,

a pumping element axially movably mounted within said reservoir and means reciprocally moving said pumping element to pump said fluid marking agent from said source into said reservoir,

said pumping element having a reduced end section adapted to be extended into and out of said feed passage upon axial movement of said pumping element to separate the fluid marking agent in said feed passage from the fluid marking agent in said reservoir and to pressurize said separated fluid marking agent,

a nozzle outlet connected with said feed passage and a check valve carried between said nozzle outlet and said feed passage with one side exposed to the pressure of the fluid marking agent in said feed passage and the opposite side exposed to atmospheric pressure at said nozzle outlet, said check valve being adapted to open automatically in response to said fluid marking agent being pressurized a predetermined amount to forcibly eject said fluid marking agent through said nozzle outlet and onto the article to be marked;

a rod extending through said housing from the end of said pumping element opposite said reduced end section,

means engaging said rod for selectively axially driving said rod into said housing for moving said pumping element and the reduced end section thereof toward and into said feed passage;

spring means engaging said pumping element and biasing said pumping element and said rod in a direction away from said feed passage; and

means carried by said rod exteriorly of said housing for adjustably limiting the axial movement of said rod into said housing to adjust the permitted stroke of said pumping element and thus the quantity of fluid marking agent ejected from said nozzle outlet.

4. The device as defined in claim 3 wherein said rod has a threaded peripheral surface, said limiting means having a threaded internal surface engaging said threaded surface of said rod whereby rotation of said limiting means relative to said rod permits adjustment of said limiting means relative to said housing. 5. The device as defined in claim 4 including means removably attached to said rod between said limiting means and said housing whereby upon removal of said last mentioned means the stroke of said plunger member can be increased without disturbing the setting of said limiting means.

6. The device as defined in claim 5 and in which said last mentioned means comprises a pin ordinarily carried by said rod intermediate said limiting means and said housing to thereby limit inward movement of said rod but removable to temporily extend the stroke of said pumping element to increase the pressure of the fluid marking agent within said feed passage whereby to blow any dried marking agent out of said nozzle outlet.

7. The device as defined in claim 3 and in which said means for driving said rod into said housing comprises an air cylinder having a piston rod connected with said rod.

8. The device as defined in claim 3 and in which said pumping element includes an enlarged portion extending radially into said reservoir and adapted to agitate the fluid marking agent contained therein when said pumping element is moved in said reservoir.

CERTIFICATE or em Patent No. 3, 9 v Dated April 4, 1972 Invent r( Paul S. Abrams, et 8,].

It is certified that error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 1, line 34, delete "application" Column 3, line 3, after "valve" delete "seam" and insert -s eat- Column 3, line 48, after "fluid" insert -is-- (SEAL) Attest:

EDWARD MQFLETCIERJR. Attesting Officer ROBERT GOITSCHALK Commissioner of Patents FORM PO-1OSO (10 59) USCOMM-DC 60376-P69 US. GOVERNMENT PRINTNG OFFICE: i969 0-366-334 

1. A device for forcibly ejecting a fluid marking agent for marking an article spaced a distance therefrom comprising: a housing having a reservoir of said fluid marking agent; a feed passage having an inlet in fluid communication with said reservoir and an outlet through which said fluid marking agent is forcibly ejected from said housing; means for closing fluid communication between said reservoir and said feed passage for separating the fluid in said feed passage for forcibly ejecting a selected amount of said separated fluid through said feed passage outlet, said means comprising a piston member movably mounted within said reservoir between a first position in which said piston member engages the inlet of said feed passage to close fluid communication between said reservoir and said feed passage; and a second position in which said piston member is spaced from said inlet to permit fluid communication between said reservoir and said feed passage; means normally biasing said piston member toward said second position; and including means for selectively varying the degree of extension of said piston member into said feed passage inlet when said piston member is in said first position; said last mentioned means comprising a stem member carried by said piston member and extending externally of said housing and means removably attached to said stem member externally of said housing, the degree of extension of said piston into said feed passage inlet being limited by the abutment of said removably attached means against said housing.
 2. A device for forcibly ejecting a fluid marking agent for marking an article spaced a distance therefrom comprising: a housing having a reservoir of said fluid marking agent; a feed passage having an inlet in fluid communication with said reservoir and an outlet through which said fluid marking agent is forcibly ejected from said housing; means for closing fluid communication between said reservoir and said feed passage for separating the fluid in said feed passage for forcibly ejecting a selected amount of said separated fluid through said feed passage outlet, said means comprising a piston member movably mounted within said reservoir between a first position in which said piston member engages the inlet of said feed passage to close fluid communication between said reservoir and said feed passage; and a second position in which said piston member is spAced from said inlet to permit fluid communication between said reservoir and said feed passage; means normally biasing said piston member toward said second position; and including means for selectively varying the degree of extension of said piston member into said feed passage inlet when said piston member is in first position; said feed passage inlet having a cross-sectional area less than the cross-sectional area of said reservoir; said piston having a shape complementary to the shape of said feed passage inlet; said feed passage inlet and said piston member being in axial alignment whereby said piston extends into and engages said feed passage inlet when said piston is in said first position, the amount of fluid ejected from said feed passage outlet being a function of the degree of extension of said piston member into said feed passage inlet at said first position of said piston, and an enlarged portion carried by said piston member, said enlarged portion extending into said reservoir and adapted to agitate the fluid marking agent contained therein when said piston member is moved to said first position.
 3. A device for forcibly ejecting a fluid marking agent for marking an article spaced a distance therefrom comprising: a housing having a reservoir for said fluid marking agent and an inlet connected with said reservoir and adapted to be connected with a source of fluid marking agent; a feed passage axially aligned with said reservoir and communicating therewith, said feed passage being of a reduced cross section as compared with said reservoir, a pumping element axially movably mounted within said reservoir and means reciprocally moving said pumping element to pump said fluid marking agent from said source into said reservoir, said pumping element having a reduced end section adapted to be extended into and out of said feed passage upon axial movement of said pumping element to separate the fluid marking agent in said feed passage from the fluid marking agent in said reservoir and to pressurize said separated fluid marking agent, a nozzle outlet connected with said feed passage and a check valve carried between said nozzle outlet and said feed passage with one side exposed to the pressure of the fluid marking agent in said feed passage and the opposite side exposed to atmospheric pressure at said nozzle outlet, said check valve being adapted to open automatically in response to said fluid marking agent being pressurized a predetermined amount to forcibly eject said fluid marking agent through said nozzle outlet and onto the article to be marked; a rod extending through said housing from the end of said pumping element opposite said reduced end section, means engaging said rod for selectively axially driving said rod into said housing for moving said pumping element and the reduced end section thereof toward and into said feed passage; spring means engaging said pumping element and biasing said pumping element and said rod in a direction away from said feed passage; and means carried by said rod exteriorly of said housing for adjustably limiting the axial movement of said rod into said housing to adjust the permitted stroke of said pumping element and thus the quantity of fluid marking agent ejected from said nozzle outlet.
 4. The device as defined in claim 3 wherein said rod has a threaded peripheral surface, said limiting means having a threaded internal surface engaging said threaded surface of said rod whereby rotation of said limiting means relative to said rod permits adjustment of said limiting means relative to said housing.
 5. The device as defined in claim 4 including means removably attached to said rod between said limiting means and said housing whereby upon removal of said last mentioned means the stroke of said plunger member can be increased without disturbing the setting of said limiting means.
 6. The device as defined in claim 5 and in which said last mentioned mEans comprises a pin ordinarily carried by said rod intermediate said limiting means and said housing to thereby limit inward movement of said rod but removable to temporily extend the stroke of said pumping element to increase the pressure of the fluid marking agent within said feed passage whereby to blow any dried marking agent out of said nozzle outlet.
 7. The device as defined in claim 3 and in which said means for driving said rod into said housing comprises an air cylinder having a piston rod connected with said rod.
 8. The device as defined in claim 3 and in which said pumping element includes an enlarged portion extending radially into said reservoir and adapted to agitate the fluid marking agent contained therein when said pumping element is moved in said reservoir. 